Information About Device Aliases

When the port WWN (pWWN) of a device must be specified to configure features (for example, zoning, DPVM, or port security) in a Cisco SAN switch, you must assign the correct device name each time you configure these features. An inaccurate device name may cause unexpected results. You can circumvent this problem if you define a user-friendly name for a pWWN and use this name in all the configuration commands as required. These user-friendly names are referred to as device aliases.

If you modify the device alias configuration, you need to commit or discard the changes as the fabric remains locked during this period.

Device alias database changes are validated with the applications. If any of the applications cannot accept the device alias database changes, then those changes are rejected; this applies to device alias database changes resulting from either a commit or merge operation.

Specifies a device name for the device that is identified by its pWWN. Starts writing to the pending database and simultaneously locks the fabric as this is the first-issued device alias configuration command.

Step 4

switch(config-device-alias-db)# no device-alias namedevice-name

Removes the device name for the device that is identified by its pWWN.

Example of Creating a Device Alias

To display the device alias configuration, use the show device-alias name command:

switch# show device-alias name x

device-alias name x pwwn 21:01:00:e0:8b:2e:80:93

Device Alias Modes

You can specify that aliases operate in basic or enhanced modes.

When operating in basic mode, which is the default mode, the device alias is immediately expanded to a pWWN. In basic mode, when device aliases are changed to point to a new HBA, for example, that change is not reflected in the zone server. Users must remove the previous HBA’s pWWN, add the new HBA’s pWWN, and then reactivate the zoneset.

When operating in enhanced mode, applications accept a device alias name in its "native" format. Instead of expanding the device alias to a pWWN, the device alias name is stored in the configuration and distributed in its native device alias format. So applications such as zone server, PSM or DPVM can automatically keep track of the device alias membership changes and enforce them accordingly. The primary benefit of operating in enhanced mode is that you have a single point of change.

Whenever you change device alias modes, the change is distributed to other switches in the network only if device alias distribution is enabled or on. Otherwise, the mode change only takes place on the local switch.

Changing Device Alias Mode Guidelines

When changing device alias modes, follow these guidelines:

If two fabrics running in different device alias modes are joined together, the device alias merge will fail. There is no automatic conversion to one mode or the other during the merge process. In this situation, you must to select one mode over the other.

Before changing from enhanced to basic mode, you must first explicitly remove all native device alias-based configurations from both local and remote switches, or, replace all device alias-based configuration members with the corresponding pWWN.

If you remove a device alias from the device alias database, all applications will automatically stop enforcing the corresponding device alias. If that corresponding device alias is part of an active zoneset, all the traffic to and from that pWWN is disrupted.

Renaming the device alias not only changes the device alias name in the device alias database, but also replaces the corresponding device alias configuration in all the applications.

When a new device alias is added to the device alias database, and the application configuration is present on that device alias, it automatically takes effect. For example, if the corresponding device alias is part of the active zoneset and the device is online, then zoning is enforced automatically. You do not have to reactivate the zoneset.

If a device alias name is mapped to a new HBA’s pWWN, then the application’s enforcement changes accordingly. In this case, the zone server automatically enforces zoning based on the new HBA’s pWWN.

Configuring Device Alias Modes

To configure device aliases to operate in enhanced mode, perform this task:

SUMMARY STEPS

1.switch# configuration terminal

2.switch(config)# device-alias mode enhanced

3.switch(config)# no device-alias mode enhance

DETAILED STEPS

Command or Action

Purpose

Step 1

switch# configuration terminal

Enters configuration mode.

Step 2

switch(config)# device-alias mode enhanced

Assigns the device alias to operate in enhanced mode.

Step 3

switch(config)# no device-alias mode enhance

Assigns the device alias to operate in basic mode.

Viewing the Device Alias Mode Setting

To view the current device alias mode setting, enter the show device-alias status command.

switch# show device-alias status

Fabric Distribution: Enabled

Database:- Device Aliases 0 Mode: Basic

Locked By:- User "admin" SWWN 20:00:00:0d:ec:30:90:40

Pending Database:- Device Aliases 0 Mode: Basic

About Device Alias Distribution

By default, device alias distribution is enabled. The device alias feature uses CFS to distribute the modifications to all switches in a fabric.

If device alias distribution is disabled, database changes are not distributed to the switches in the fabric. The same changes would have to be performed manually on all switches in the fabric to keep the device alias database up-to-date. Database changes immediately take effect, so there would not be any pending database and commit or abort operations either. If you have not committed the changes and you disable distribution, then a commit task will fail.

The following example displays a failed device alias status:

switch# show device-alias status

Fabric Distribution: Disabled

Database:- Device Aliases 25

Status of the last CFS operation issued from this switch:

==========================================================

Operation: Commit

Status: Failed (Reason: Operation is not permitted as the fabric distribution is

currently disabled.)

Locking the Fabric

When you perform any device alias configuration task (regardless of which device alias task), the fabric is automatically locked for the device alias feature. Once you lock the fabric, the following situations apply:

No other user can make any configuration changes to this feature.

A copy of the effective database is obtained and used as the pending database. Subsequent modifications are made to the pending database. The pending database remains in use until you commit the modifications to the pending database or discard (abort) the changes to the pending database.

Committing Changes

If you commit the changes made to the pending database, the following events occur:

The pending database is distributed to the switches in the fabric and the effective database on those switches is overwritten with the new changes.

The pending database is emptied of its contents.

The fabric lock is released for this feature.

To commit the changes, perform this task:

SUMMARY STEPS

1.switch# configuration terminal

2.switch(config)# device-alias commit

DETAILED STEPS

Command or Action

Purpose

Step 1

switch# configuration terminal

Enters configuration mode.

Step 2

switch(config)# device-alias commit

Commits the changes made to the currently active session.

Discarding Changes

If you discard the changes made to the pending database, the following events occur:

The effective database contents remain unaffected.

The pending database is emptied of its contents.

The fabric lock is released for this feature.

To discard the device alias session, perform this task:

SUMMARY STEPS

1.switch# configuration terminal

2.switch(config)# device-alias abort

DETAILED STEPS

Command or Action

Purpose

Step 1

switch# configuration terminal

Enters configuration mode.

Step 2

switch(config)# device-alias abort

Discards the currently active session.

Displaying the Status of a Discard Operation

To display the status of the discard operation, use the show device alias status command.

switch# show device-alias status

Fabric Distribution: Enabled

Database:- Device Aliases 24

Status of the last CFS operation issued from this switch:

==========================================================

Operation: Abort

Status: Success

Fabric Lock Override

You can use locking operations (clear, commit, abort) only when device alias distribution is enabled. If you have performed a device alias task and have forgotten to release the lock by either committing or discarding the changes, an administrator can release the lock from any switch in the fabric. If the administrator performs this task, your changes to the pending database are discarded and the fabric lock is released.

The changes are only available in the volatile directory and may be discarded if the switch is restarted.

To use administrative privileges and release a locked device alias session, use the clear device-alias session command in EXEC mode.

switch# clear device-alias session

To display the status of the clear operation, use the show device-alias status command.

switch# show device-alias status

Fabric Distribution: Enabled

Database:- Device Aliases 24

Status of the last CFS operation issued from this switch:

==========================================================

Operation: Clear Session<--------------------Lock released by administrator

Status: Success<-----------------------------Successful status of the operation

Disabling and Enabling Device Alias Distribution

To disable or enable the device alias distribution, perform this task:

SUMMARY STEPS

1.switch# configuration terminal

2.switch(config)# no device-alias distribute

3.switch(config)# device-alias distribute

DETAILED STEPS

Command or Action

Purpose

Step 1

switch# configuration terminal

Enters configuration mode.

Step 2

switch(config)# no device-alias distribute

Disables the distribution.

Step 3

switch(config)# device-alias distribute

Enables the distribution (default).

Viewing the Status of Device Alias Distribution

To display the status of device alias distribution, use the show device-alias status command. The following example shows the device alias display when distribution is enabled:

The following example shows the device alias display when distribution is disabled:

switch# show device-alias status

Fabric Distribution: Disabled

Database:- Device Aliases 24

Status of the last CFS operation issued from this switch:

==========================================================

Operation: Disable Fabric Distribution

Status: Success

About Legacy Zone Alias Configuration

You can import legacy zone alias configurations to use this feature without losing data if they satisfy the following restrictions:

Each zone alias has only one member.

The member type is pWWN.

If any name or definition conflict exists, the zone aliases are not imported.

Ensure that you copy any required zone aliases to the device alias database as required by your configuration.

When an import operation is complete, the modified alias database is distributed to all other switches in the physical fabric when you perform the commit operation. If you do not want to distribute the configuration to other switches in the fabric, you can perform the abort operation and the merge changes are completely discarded.